1. Field
Embodiments relate to a brushless direct current (BLDC) motor driving apparatus which achieves power-saving operation of a refrigerator, and a refrigerator using the same.
2. Description of the Related Art
In general, a brushless direct current (BLDC) motor uses an inverter circuit including switching elements instead of mechanical elements, such as a brush and a commutator, and is characterized in that replacement of a brush due to abrasion of the brush is not required and electromagnetic interference and noise are minimal.
Such a BLDC motor has been widely used in products requiring high-frequency and variable-speed operation, such as a compressor for refrigerators and air conditioners, and a washing machine.
In order to operate the BLDC motor, flux of a stator needs to be controlled so as to have a right angle or a random angle to flux of a permanent magnet generated from a rotor. For this purpose, the position of the rotor is detected at all times, and the switching state of the switching elements of the inverter is determined so that a flux generating position of the stator is determined according to the position of the rotor. Here, in order to detect the position of the rotor, a resolver, an absolute encoder, or a hall sensor may be used. In case of a compressor for refrigerators and air conditioners, use of a sensor is difficult due to environmental factors, such as temperature and pressure, and thus a sensorless type in which the position of a rotor is detected from voltage or current applied to a motor is mainly used. In general, a sensorless BLDC motor detects the position of a rotor using back electromotive force (back-EMF) of a motor detected through a position detection circuit.
In order to control the rotating speed of the BLDC motor, a pulse width modulation (PWM) method is generally used. That is, driving current applied to the motor is adjusted by inputting driving current, the pulse width of which is modulated, and the rotating speed of the BLDC motor is controlled through the adjusted driving current.
In order to reduce energy consumption, low-speed operation in which a motor used in a compressor for refrigerators or air conditioners is rotated at a low speed is required, and in order to achieve such low-speed operation, the duty of a pulse needs to be decreased.
If the pulse duty of driving current applied to the BLDC motor is very small, detection of the position of the rotor may be difficult.